JP3880831B2 - Ink preset method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink preset method for adjusting the amount of ink remaining on an ink roller before the next printing operation in a printing apparatus that performs printing such as offset printing.
[0002]
[Prior art]
A general offset printing apparatus is provided with an ink fountain apparatus having a plurality of ink keys, and the ink supply amount can be varied along the width direction of the printing paper. As a result, according to the image area on the printing plate, the ink supply amount is increased so that the ink supply amount is increased where the image area is large, that is, where the ink consumption is large, and conversely, the ink supply amount is decreased when the ink area is small. The distribution was controlled.
[0003]
By the way, as one printing operation, when one printing operation is completed, the printing plate is usually replaced and the next printing operation is performed. In this case, since the printed image is different between the previous work and the current work, the ink supply amount must be adjusted again.
[0004]
However, the amount of ink remaining on the ink roller after completion of the previous operation is often non-uniform based on the image area distribution at the previous operation, so the distribution of new ink amount in a short time at the start of the next printing. Therefore, there is a problem that it takes a long time to consume a large amount of waste paper before the printing quality is stabilized at the next printing.
[0005]
[Problems to be solved by the invention]
In order to solve the above problems, for example, a technique as disclosed in Japanese Patent Application Laid-Open No. 10-16193 is known. In this prior art, printing is performed with the ink supply stopped, and the ink remaining on the ink roller is reduced to the minimum necessary amount. That is, the unevenness of the distribution of the ink amount on the ink roller, which has occurred in the previous printing operation, is deleted so as to be uniform by transferring the ink to the printing paper. Then, new ink is supplied before the next printing to complete the ink preset.
[0006]
Although this prior art is effective, there is a problem that it is necessary to use useless printing paper (spreading paper) before ink can be deleted. In particular, when handling a relatively high density image during the previous printing and handling a relatively low density image in the next operation, it is necessary to remove a lot of ink, and it takes a relatively long time to complete the ink preset. Yare paper tends to be needed.
[0007]
The present invention provides a new ink presetting method that eliminates the unevenness of the ink amount distribution on the ink roller in advance.
[0008]
[Means for Solving the Problems]
  The invention according to claim 1 is an ink fountain device capable of changing the amount of ink supplied to a plurality of ink key regions in the printing width direction, and an ink roller group for transferring ink supplied by the ink fountain device to a printing plate surface. An ink preset method for metering the amount of ink remaining in the ink roller group before the start of the next printing, from a printed image on a printing paperAboveA first printing step of measuring the measured print density Xn for the ink key area and performing printing while adjusting the ink supply amount of each ink key area so that the measured print density Xn matches the first target density V1; After the first printing step, the first target density V1 is changed to a second target density V2 that is lower than the first target density V1, and the measured print density Xn becomes the second target density V2. A second printing step for performing printing while adjusting the ink supply amount of each ink key region so as to match, and the printing apparatus after the measured printing density Xn matches the target density V2 by the second printing step It is characterized by stopping.
[0009]
A second aspect of the present invention is the ink presetting method according to the first aspect, characterized in that a density measuring device for measuring a print density on the printing paper is provided on the printing apparatus.
[0010]
A third aspect of the present invention is the ink presetting method according to the first or second aspect, wherein the measured print density Xn is made to coincide with at least the second target density V2 within ± 0.2. It is characterized by that.
[0011]
The invention according to claim 4 is the ink preset method according to any one of claims 1 to 3, wherein the second target density V2 is set in a range of V1> V2 ≧ (V1-0.2). It is characterized by that.
[0012]
A fifth aspect of the present invention is the ink presetting method according to any one of the first to fourth aspects, wherein the measured print density Vn is stored in association with every predetermined number of sheets or every predetermined work time and displayed as a history. It is characterized by doing so.
[0013]
  A sixth aspect of the present invention is the ink presetting method according to any one of the first to fifth aspects, wherein after the printing apparatus is stopped and before the next printing, a constant ink key opening degree is set for each ink key area. A first replenishment step of replenishing a predetermined amount of ink to the ink roller group, and an ink key opening degree corresponding to an image of the next printing for each ink key region,AboveA second replenishing step of replenishing ink to the ink roller group.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
[Description of printing device]
Embodiments of a printing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an example of a printing apparatus for realizing the pre-ink method according to the present invention. First, as shown in FIG. 1, the printing apparatus includes, as printing mechanisms, first and second plate cylinders 1 and 2 for holding a printing plate, and first and second plates for transferring an ink image from each plate cylinder. Second blanket cylinders 3, 4, a pressure cylinder 5 that holds printing paper and an ink image is transferred from both blanket cylinders 3, 4, and a paper feed cylinder 6 that supplies or discharges printing paper to and from the impression cylinder 5 The paper discharge cylinder 7, the dampening water supply means 8 for supplying dampening water or ink to the printing plates on the first and second plate cylinders 1 and 2, and the ink supply means 9, A paper supply unit 10 that sequentially supplies printing paper for printing and a paper discharge unit 11 that sequentially stacks printed printing papers are provided.
[0021]
On the other hand, this printing apparatus has, as a plate making mechanism, a printing plate supply unit 12 for supplying an unexposed printing plate to the first and second plate cylinders 1 and 2 and an image on the printing plate on the plate cylinder. An image recording unit 13 for recording, a developing unit 14 for developing a printing plate on which an image is recorded, and a printing plate discharge unit 15 for discharging a used printing plate are provided.
[0022]
The printing apparatus also has an image reading apparatus 16 for measuring an image density by taking an image on a printed printing paper, a cleaning apparatus 17 for cleaning the blanket cylinder, and a control for controlling the entire printing apparatus. Device 18.
[0023]
Hereinafter, the details of each of the above portions will be described. The first plate cylinder 1 is configured to be movable between a first printing position indicated by a solid line in FIG. 1 and an image recording position indicated by a two-dot chain line by a plate cylinder driving mechanism (not shown). Similarly, the second plate cylinder 2 is configured to be movable between a second printing position indicated by a solid line in FIG. 1 and an image recording position indicated by a two-dot chain line by a plate cylinder driving mechanism (not shown). That is, the first and second plate cylinders 1 and 2 are respectively arranged at the first or second printing position when the printing operation is executed, and are alternately arranged at the image recording position when the plate making operation is executed. Then, the plate making process of the printing plate on each plate cylinder is performed. Each of the first plate cylinder 1 and the second plate cylinder 2 has a circumferential surface capable of holding printing plates for two colors, and the printing plates are fixed at positions facing each other by 180 degrees on the circumferential surface. There is a customizing means for doing this.
[0024]
The first blanket cylinder 3 is configured to rotate in contact with the first plate cylinder 1 at the first printing position, and the second printing position is similarly applied to the second blanket cylinder 4. In FIG. 2, the second plate cylinder 2 is configured to contact and rotate. The first and second blanket cylinders 3 and 4 have the same diameter as the first and second plate cylinders 1 and 2, and blankets capable of transferring ink images of two colors from the respective plate cylinders. It is mounted on the circumference.
[0025]
The impression cylinder 5 has a diameter half that of the first and second plate cylinders 1 and 2 and is configured to rotate in contact with both the first and second blanket cylinders 3 and 4. ing. The impression cylinder 5 is provided with a gripping means capable of holding one printing sheet having a size corresponding to the printing plate. The gripping means can be opened / closed at a predetermined timing by an opening / closing mechanism (not shown) to hold the front end portion of the printing paper.
[0026]
The paper feed cylinder 6 and the paper discharge cylinder 7 have the same diameter as the impression cylinder 5, and are provided with a gripping means (not shown) similar to the gripping means provided on the impression cylinder 5. The gripping means of the paper feed cylinder 6 is arranged so as to deliver the printing paper in synchronism with the gripping means of the pressure drum 5, and the gripping means of the paper discharge cylinder 7 is the collar of the pressure drum 5. The printing paper is arranged to be received in synchronization with the printing means.
[0027]
The first and second plate cylinders 1 and 2 disposed at the first and second printing positions, the first and second blanket cylinders 3 and 4, the impression cylinder 5, the paper feed cylinder 6 and the discharge cylinder. The paper cylinder 7 is rotationally driven in synchronism with a print driving motor (not shown). In the printing apparatus according to the present embodiment, the plate cylinders 1 and 2 and the blanket cylinders 3 and 4 have a circumferential length twice that of the impression cylinder 5, so that the plate cylinders 1 and 2 and the blanket cylinders 3 and 4 are 1 Each time it rotates, the impression cylinder rotates twice. Accordingly, when the impression cylinder 5 is rotated twice while holding the printing paper, the first and second plate cylinders 1 and 2 can perform multicolor printing of a total of four colors of 2 colors + 2 colors.
[0028]
Two sets of dampening water supply means 8 are arranged for each of the plate cylinders 1 and 2 at the first and second printing positions, and are selective to the two printing plates on each of the plate cylinders 1 and 2. Can be supplied with dampening water. The dampening water supply means 8 includes a water boat that stores dampening water and a dampening water roller group that pumps up the dampening water in the water boat and passes it to the printing plate surface. The roller that contacts the plate surface is configured to contact or separate from the plate cylinder surface by a cam mechanism. If the printing plate is a type of printing plate that does not require fountain solution, the fountain solution supply means 8 is not necessary.
[0029]
Two sets of ink supply means 9 are arranged for each of the plate cylinders 1 and 2 in the first and second printing positions, and are selectively different for the two printing plates on the plate cylinders 1 and 2. Color ink can be supplied. The ink supply means 9 includes ink fountain means capable of adjusting the ink supply amount for each of a plurality of regions in the printing width direction, and the ink discharged from the ink fountain means is transferred to the plate cylinder via a plurality of rollers. It is supplied to the upper printing plate. Details of the ink supply means 9 will be described later.
[0030]
The ink of each ink supply means 9 is, for example, arranged for the first plate cylinder 1 with K (black) and M (magenta) ink supply means 8 and for the second plate cylinder 2. Thus, ink supply means 8 for C color (cyan) and Y color (yellow) are arranged. Further, some of the fountain solution supply means 8 and the ink supply means 9 are configured such that they can be withdrawn from their movement paths as the first and second plate cylinders 1 and 2 move.
[0031]
The paper feeding unit 10 takes out printing paper one by one from a pile on which unused printing paper is stacked and passes it to the paper feeding cylinder 6. In this embodiment, the paper feeding unit 1 is turned on every two rotations of the paper feeding cylinder. Operates to supply twice-printed paper. On the other hand, the paper discharge unit 11 receives printed paper from the paper discharge cylinder 7 and stacks it. The paper discharge unit 11 is composed of a known chain conveyance mechanism, and discharges and conveys the print paper by holding the leading end portion of the printing paper with a gripping claw circulated by the chain. An image reading device 16 is provided in the movement path along which the printed matter is discharged by the paper discharge unit 11.
[0032]
Next, the plate making mechanism of this printing apparatus will be described. In this printing apparatus, when the plate making operation is executed, the first and second plate cylinders 1 and 2 are alternately moved to the image recording position. At this image recording position, a friction roller (not shown) is configured to abut on the plate cylinder and rotate.
[0033]
The printing plate supply unit 12 includes a cassette roll that stores a roll-shaped unexposed printing plate in a shaded state, a conveyance roller and a conveyance guide that conveys the drawn printing plate to the plate cylinders 1 and 2, and the printing plate in a sheet form Cutting means. In this embodiment, a silver salt sensitive material is used as the printing plate, and an image is recorded by laser light. The printing plate supply operation procedure is as follows. First, the front end of the printing plate drawn out from the cassette roll is sandwiched between gripping means (not shown) of the printing cylinders 1 and 2, and the printing cylinders 1 and 2 are rotated in this state to perform printing. The plate is wound on the plate cylinders 1 and 2, and then the printing plate is cut to a predetermined length and the rear end of the printing plate is held by the other gripping means.
[0034]
The image recording unit 13 records the image on the printing plate by exposing the printing plate by turning on / off the laser beam. In this embodiment, the position of the image on the printing plate is determined by the control device 18, and the corresponding image data is sent to the image recording unit 13. In the image recording unit 13, the laser beam emitted from the laser transmission source is subjected to main scanning along the axial direction of the plate cylinder by a polarizer such as a polygon mirror, and the printing plate surface is sub-scanned by rotating the plate cylinder. It is configured. The scanning method may be a type in which a plurality of laser beams are provided in the plate cylinder axis direction and main scanning is performed as the plate cylinder rotates. Further, the printing plate and the image recording unit 13 may record not only an image by exposure but also an image by heat or other processing.
[0035]
The developing unit 14 develops the printing plate exposed by the image recording unit 13. In this embodiment, the developing unit 14 is configured to draw up the processing liquid stored in the processing tank by a coating roller and apply it to the printing plate to perform the developing process. Lifting means for moving to a position close to the trunk is provided. If an image recording method that does not require development processing is employed, the developing unit 14 may not be provided.
[0036]
In this printing apparatus, the first and second plate cylinders 1 and 2 are moved to the image recording position, and the plate making operation is performed by supplying the printing plate and recording and developing the image. When the plate making operation is completed, the first and second plate cylinders 1 and 2 can be arranged at the first and second printing positions to perform the printing operation.
[0037]
On the other hand, the printing apparatus can automatically discharge the printing plate after the printing operation is completed. In this embodiment, the printing plate discharge unit 15 includes a peeling unit that peels the printing plate from the plate cylinder at the image recording position, a conveyance unit that conveys the peeled printing plate, and a used printing plate that has been conveyed. A discharge cassette.
[0038]
The image reading device 16 includes a CCD line sensor that captures the printing paper being ejected in line order and obtains desired image data. In this embodiment, the RGB image data obtained by the image reading device 16 can be converted into CMYK image density values by the control device 18 to measure the print density on the printing paper. For example, in this embodiment, a plurality of color chart images are formed on the printing plate along the printing width direction. Since this color chart image includes a solid patch image provided corresponding to each ink key area, four color solid patches of YMCK are printed in each ink key area on the printing paper. Therefore, the image density of each ink key area can be measured by taking an image of the solid patch and measuring the print density.
[0039]
The cleaning device 17 contacts the blanket cylinder and cleans the surface of the cylinder. In this embodiment, each of the blanket cylinders 3 and 4 is provided with an individual cleaning device. The cleaning device 17 includes a cleaning liquid supply unit and a wiping unit using a cleaning cloth.
[0040]
The control device 18 is a microcomputer system including various input / output means and storage means, and is stored inside the printing apparatus. The control device 18 performs arithmetic processing of the image read by the image reading device 16 based on a predetermined program operation and controls the entire printing device. Therefore, the control device 18 also performs control for adjusting the ink supply amount in the ink presetting method according to the present invention.
[0041]
Next, the detailed configuration of the ink supply means 9 in the present invention and the principle of the ink presetting method will be described. FIG. 2 is a schematic diagram showing a path through which ink is transferred from the ink supply means 9 to the printing paper. In the figure, first, the ink supply means 9 includes an ink fountain means 21, an ink call roller 23 for delivering ink from the ink fountain means 21 to the downstream ink roller 22, and the ink transferred from the ink roller 22 to the plate cylinder. And an ink form roller 24 that is attached to the upper and lower printing plate surfaces.
[0042]
The ink fountain means 21 includes a rotatable ink base roller 25 and an ink key 26 that is close to the ink base roller 25 at a minute interval, and is surrounded by the ink base roller 25, the ink key 26, and a side plate (not shown). An ink reservoir i is formed in the ink groove. In the ink fountain means 21, the ink key 26 is divided into a plurality of parts along the axial direction of the ink source roller 25, and each of them is independently spaced from the circumferential surface of the ink source roller 25 (hereinafter, the ink key opening degree). It is configured to be adjustable. When the ink base roller 25 rotates counterclockwise in the figure in this state, an ink film having a desired thickness is formed on the surface of the ink base roller 25 according to the opening degree of the ink key 26. Hereinafter, the divided area of each ink key is referred to as an ink key area.
[0043]
The ink roller 22 is formed by continuously abutting a plurality of metal or rubber ink rollers (only one is shown in the figure) and sequentially transfers ink. The ink calling roller 23 is configured to reciprocate between the ink original roller 25 and the ink roller 22 so as to contact each other alternately. That is, the ink on the ink base roller 25 can be transferred to the ink roller 22 by the reciprocation of the ink calling roller 23. Hereinafter, the number of reciprocations of the ink call roller 23 is referred to as the number of ink calls.
[0044]
The ink form roller 24 transfers the ink kneaded by the ink roller 22 onto the printing plate surface. In this embodiment, the plate cylinder 1 is formed by a cam mechanism so as to contact only the corresponding printing plate surface. 2 is configured to move up and down. The ink roller 22 to the ink form roller 24 are collectively referred to as an ink roller group.
[0045]
In this ink supply means 9, the ink supply amount in each ink key region along the printing width direction can be varied by adjusting each of the ink keys 26. Further, the increase / decrease of the total ink supply amount can be adjusted by the number of calls of the ink call roller 23. For example, if the reciprocation of the ink calling roller 23 is stopped, the ink supply from the ink fountain means 21 to the ink roller 22 can be prevented.
[0046]
The ink transferred to the printing plate surface by the ink supply means 9 is transferred to the printing paper on the impression cylinder 5 via the blanket cylinders 3 and 4. The blanket cylinders 3 and 4 are configured to selectively abut against or separate from the plate cylinders 1 and 2 and the impression cylinder 5 by a so-called cylinder-inserting cylinder removing mechanism 27 that decenters the blanket cylinders 3 and 4. Has been.
[0047]
[Explanation of ink amount and printing density]
Next, the correlation between the ink amount and the printing density related to the preset method of the present invention will be described. First, when the ink transfer state from the ink supply means 9 to the printing paper is analyzed by simulation, “if the printing density of the printed matter is kept constant, the ink supply amount a from the ink fountain means 21 to the ink roller group and the ink It was found that the amount of ink consumed b from the roller group to the printing plate surface was balanced, and the total amount of ink remaining in the ink roller group was substantially constant. This phenomenon will be described with reference to the experimental results of FIGS.
[0048]
First, FIGS. 6 to 8 are graphs showing changes in the amount of ink when printing is performed with different image areas of 10%, 30%, and 50%, respectively, and the printing density is controlled to maintain an appropriate value. The ink amount is represented by a cross-sectional area (1/1000 square mm) calculated by the ink film thickness on the ink roller × the roller circumference.
[0049]
In the figure, the dotted line indicates the ink transfer amount A (same as the ink supply amount a) in units of one sheet transferred from the ink fountain means 21 to the ink roller group. (Scale on the left side of the graph) The transfer amount A to the ink roller group is maximum immediately after the start of printing, but since the ink amount held in the ink roller group increases sequentially, the transfer amount A decreases gradually. It becomes an equilibrium state.
[0050]
An alternate long and short dash line in the figure indicates an ink transfer amount B (same as the ink consumption amount b) in units of one sheet from the ink roller group to the printing plate surface. (Scale on the left side of the graph) The transfer amount B with respect to the printing plate surface is 0 at the start of printing, and increases every time ink is supplied to reach an equilibrium state.
[0051]
The solid line in the figure indicates the total ink amount C held in the ink roller group. (Scale on the right side of the graph) The total ink amount C is 0 at the start of printing, and increases every time ink is supplied to reach an equilibrium state. If the printing density is controlled to a constant value, the total ink amount C is in a balanced state between the transfer amount A and the transfer amount B and converges to a constant value. The total ink amount C is almost the same value if the printing density is the same, as can be determined from the graph. That is, if the printing density is controlled to be constant, the ink supply amount and the consumption amount are balanced, and the total ink amount C held by the ink roller group is kept substantially constant regardless of the image area.
[0052]
Next, FIGS. 9 and 10 show changes in the ink amount when printing is performed with the same image area of 30% and the printing density is controlled to be maintained at the appropriate density of −0.2 and the appropriate density of +0.2, respectively. It is a graph, and the dotted line, the dashed-dotted line, and the continuous line in a figure represent the same item as FIGS. As shown in this figure, the value of the total ink amount C held in the ink roller group changes by increasing or decreasing the target print density.
[0053]
In view of the above characteristics, if the ink supply control is performed so that the print densities in all the ink key areas are always the same, a substantially constant amount of ink remains on the ink roller in the axial direction. The first feature of the present invention is that the amount of ink remaining on the ink roller is made substantially constant by the above method.
[0054]
In this embodiment, the print density to be adjusted is controlled by the measured density of the solid patch provided for each ink key area. As a result of examination by the present applicant, the print density range is ± 0.2 from the target print density. It has been found that the adjustment may be made within the range, preferably ± 0.1, and more preferably ± 0.05. If there is a print density difference greater than this, the change in the amount of ink remaining in the ink roller group becomes large as shown in FIGS. There is a need to do.
[0055]
Note that the print density is measured in real time as much as possible, and feedback of ink supply control is preferably performed without delay. In such a case, it is difficult to cope with the method in which a conventional operator manually extracts and inspects, and if the sampling inspection is frequently performed, it is inconvenient because it is necessary to increase the number of required prints. Therefore, it is desirable that the printing density measuring device be installed on the printing press as in this embodiment.
[0056]
As described above, in the present invention, the amount of ink held by the ink roller group can be made constant by strictly controlling the printing density. However, the ink transfer amounts A and B supplied or consumed for each printing paper differ depending on the size of the printed image area, and the ink amounts corresponding to the transfer amounts A and B for each sheet are actually Are distributed with a predetermined inclination from the upstream roller to the downstream roller of the ink roller group. Although the amount corresponding to the inclination is small compared with the total amount of ink held in the ink roller group, even if the printing density is controlled to a predetermined value, only the amount corresponding to the inclination is obtained. It is assumed that the amount of ink to be held increases. Therefore, the second feature of the present invention is that it includes a step of reducing the print density at the end of printing so that the amount of remaining ink is slightly reduced.
[0057]
[Description of Ink Preset Method (First Embodiment)]
Next, the procedure of the ink preset method according to the present invention will be described with reference to FIGS. FIG. 3 is a flowchart according to the first embodiment of the ink presetting method.
[0058]
In FIG. 3, in step S1, the target print density V1 is set. For example, when using a general coated paper, the target print density V1 is about 1.3 to 1.8 depending on the print color, and is the same along the width direction of the print paper. In the next step S2, the opening degree is adjusted for each ink key 26 in accordance with the image area of the image to be printed. In step S3, printing is started. Of course, before actual printing is started, the dampening printing or the like may be performed by appropriately adjusting the amount of dampening water or ink.
[0059]
If printing can be performed on the printing paper, in step S4, the printing density Vn is measured for each color and each ink key area. As described above, this is obtained by reading the solid patch of each color printed on the printing paper with the image reading device 16 and converting the RGB value of the read image data into the density of YMCK.
[0060]
In step S5, it is determined whether the necessary number of prints has been obtained. If printing has not been completed, the process returns to step S3 via step S6. In step S6, it is compared whether or not the measured print density Vn matches the target print density V1, and if it is different, the opening degree of the ink key is adjusted according to the difference. In this embodiment, Vn may be in the range of V1 ± 0.2.
[0061]
The feedback control in step S6 is set at a desired interval, that is, at intervals of 1 to several tens of printing sheets. If it is determined that the print quality is stable and good, the number of printed sheets is counted. If it is determined in step S5 that the required number of sheets have been printed, the process proceeds to step S7.
[0062]
In step S7, the target print density is changed to V2. It has been experimentally found that the target print density V2 may be set in a range of V1> V2 ≧ (V1-0.2), and preferably the target print density V2 is set to 0.1 or 0.1 from V1. Set to a value as low as 2. In step S8, the ink supply amount is adjusted according to the setting of the new target print density V2. Here, the opening degree of each ink key may be adjusted again. However, in order to uniformly reduce the density in the entire region, the rotation speed of the ink source roller 25, the number of calls of the ink calling roller 23, and the like are adjusted. Also good. Of course, you may make it combine the said several adjustment method.
[0063]
In step S9, printing is performed, and in step S10, the print density is measured. In step S11, it is determined whether or not the measured print density Vn matches the target print density V2, and if it matches, this flow ends. If they do not match, the process is fed back to step S8.
[0064]
In this ink preset method, the normal first printing process is performed in steps S1 to S6, and at this time, the printing density of each ink key area is made to coincide with the target printing density V1. As a result, the amount of ink held by the ink roller group at the end of printing can be made substantially constant. Then, in the next steps S7 to S11, the printing density is lowered to V2 and the second printing process is performed, whereby the ink amount held by the ink roller group is slightly reduced from the ink amount in the first printing process. Can be terminated.
[0065]
According to this method, at the end of printing, a small amount of ink with a constant thickness remains in each area in the ink roller group, and since the ink distribution is stable, printing can be performed quickly in the next operation. In this method, since the print density control is performed in the first printing process in advance, the adjustment work in the second printing process is easy, and very little printing paper is consumed during this time. In addition, since the printing in the second printing step has only a slightly lower printing density than the first printing step, it can be used as an original printed matter if it is determined that the quality is acceptable.
[0066]
[Second Embodiment]
Since the ink preset method described above uses printing paper in the second printing step, there is a possibility that waste paper may be generated. The second embodiment described below is a method for realizing a reduction in printing density by transferring ink to a plate cylinder or a blanket cylinder without using printing paper, and FIG. 4 is a flowchart thereof.
[0067]
In FIG. 4, steps S1 to S6 are the same as those in the first embodiment, and thus description thereof is omitted. In the second embodiment, first, in step S20, ink supply is stopped and printing paper supply is stopped. The stop of the ink supply can be realized by stopping the call operation of the ink call roller 23. Further, the blanket cylinders 3 and 4 are removed from the impression cylinder 5 as the printing paper supply is stopped.
[0068]
In step S21, the plate cylinder is rotated in a state where the ink form roller 24 is in contact with the printing plate surface, and the ink on the ink roller group is transferred to the printing plate surface. In the experiment, when the plate cylinder is rotated about three times, an effect substantially equivalent to the decrease in the printing density performed in the first embodiment is obtained, and there is an effect of approximately -0.1 in terms of the printing density. . After the ink transfer is completed, the contact state between the ink roller and the plate cylinder may be released, and then the plate cylinders 1 and 2 may be brought into contact with the blanket cylinders 3 and 4 and rotated. In this case, the ink transferred to the plate cylinders 1 and 2 can be dispersed in the blanket cylinder.
[0069]
If the blanket cylinder is brought into contact with the plate cylinder during the ink transfer, not after the ink transfer is completed, the amount of ink transfer increases, and there is an effect of about -0.2 in terms of printing density. all right.
[0070]
In step S22, the printing plate to which the ink has been transferred is discharged. The blanket cylinder to which the ink has been transferred is washed by the washing device 17. In addition, when there is a problem at the time of discharging and conveying the printing plate due to ink adhesion, the printing plate may be washed and then discharged. For example, in the simplest example, when the plate cylinders 1 and 2 are brought into contact with the blanket cylinders 3 and 4 when the cleaning device 17 cleans the blanket cylinders 3 and 4, the printing plate is also indirectly cleaned. be able to. Since the degree of cleaning of the printing plate may be low, it may be performed simultaneously in the first half of the cleaning process of the blanket cylinders 3 and 4.
[0071]
[Third embodiment]
In the above-described embodiment, as an ink presetting method, the ink remaining before the next printing is uniformly and lowered in the ink roller group. Actually, the ink must be supplied in accordance with the new image area distribution at the time of the next printing. This method will be described with reference to the flowchart of FIG.
[0072]
First, in step S31, an ink amount to be newly supplied is set. However, the adjustment of the ink amount here is set by the number of calls of the ink call roller 23. For example, in the case of the first embodiment, the number of calls in the following steps S33 and S35 is set according to the print density difference (V1-V2). In the case of the second embodiment, the number of calls in the following steps S33 and S35 is set according to the amount of transfer to the printing plate or blanket cylinder that is experimentally known in advance.
[0073]
First, in step S32, the opening degree of all ink keys is set uniformly, for example, about 75% here. In step S33, ink is supplied for the number of calls set in step S31 in this state. In this embodiment, when the print density is reduced by -0.1 in the first embodiment, the number of ink calls is about 6 times at an opening degree of 75%.
[0074]
Next, in step S34, the opening degree of the ink key is adjusted according to the image area of the next printing. In step S35, ink is supplied in this state. Here, the number of ink calls is about three. According to this procedure, after the first or second embodiment, the uniformly reduced ink amount can be adjusted to the ink amount necessary for the next printing operation. In the adjustment of the ink amount described above, the adjustment is performed mainly based on the number of calls of the ink call roller 23, but other parameters such as the rotation amount of the ink base roller may be adjusted. .
[0075]
[Other embodiments]
The present invention is not limited to the above-described embodiment, and can be implemented in various forms. For example, a general offset printing apparatus that does not include a plate-making mechanism or a waterless lithographic printing apparatus that does not use dampening water can be employed.
[0076]
The printing density measuring device may be provided outside the machine, but it is preferable that the printing density measuring apparatus is provided on the machine for the reasons described above and feedback can be applied in real time. As an additional advantage in this case, the density history management of the printed matter can be easily performed. For example, FIG. 11 is a graph showing a change in printing density in a predetermined color and ink key area. That is, if the measured print density Vn is recorded every predetermined number of sheets or every predetermined time, such data can be displayed or printed out and used as management data for printed matter.
[0077]
The print density is preferably measured based on a solid patch applied to each ink key area, but a specific part on a preset image may be measured.
[0078]
【The invention's effect】
  According to the present invention, the amount of ink remaining on the ink roller can be made substantially uniform by making the printing density constant. This makes it easy to print out the next operation..
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of a printing apparatus capable of executing an ink preset method used in the present invention.
FIG. 2 is a schematic diagram showing an outline of an ink supply means and an ink transfer path.
FIG. 3 is a flowchart showing an ink preset method according to the first embodiment.
FIG. 4 is a flowchart illustrating an ink preset method according to a second embodiment.
FIG. 5 is a flowchart showing a new ink supply procedure after the ink amount on the ink roller is reduced to a certain level.
FIG. 6 is a graph showing the transition of the ink transfer amount.
FIG. 7 is a graph showing the transition of the ink transfer amount.
FIG. 8 is a graph showing changes in the amount of ink transfer.
FIG. 9 is a graph showing the transition of the ink transfer amount.
FIG. 10 is a graph showing the transition of the ink transfer amount.
FIG. 11 is a graph showing a print density history.
[Explanation of symbols]
1 First plate cylinder
2 Second plate cylinder
3 The first blanket cylinder
4 Second blanket cylinder
5 impression cylinder
16 Image reader
17 Cleaning device
18 Control device
21 Ink fountain means
22 Ink roller
23 Ink call roller
24 Inking roller
V1 First target print density
V2 Second target print density
Vn measurement printing density

Claims (6)

In a printing apparatus comprising an ink fountain device capable of varying the amount of ink supplied to a plurality of ink key areas in the printing width direction, and an ink roller group for transferring ink supplied by the ink fountain device to the printing plate surface, the next printing An ink preset method for metering the amount of ink remaining in the ink roller group before starting,
Measurement print density Xn with respect to the ink key regions measured from the printed image on the printing paper, performs printing while adjusting the ink supply amount of each ink key area, as this measure print density Xn matches the first target concentration V1 A first printing step;
After the first printing step, the first target density V1 is changed to a second target density V2 that is lower than the first target density V1, and the measured print density Xn is set to the second target density V2. A second printing step of performing printing while adjusting the ink supply amount of each ink key region so as to match
An ink preset method, wherein the printing apparatus is stopped after the measured print density Xn matches the target density V2 in the second printing step.   The ink preset method according to claim 1, further comprising: a density measuring device that measures a printing density on the printing paper on the printing apparatus.   3. The ink preset method according to claim 1, wherein the measured print density Xn is made to coincide with at least the second target density V2 within ± 0.2.   4. The ink preset method according to claim 1, wherein the second target density V2 is set in a range of V1> V2 ≧ (V1-0.2).   The ink preset method according to any one of claims 1 to 4, wherein the measured print density Vn is stored in association with every predetermined number of sheets or every predetermined work time and displayed as a history. After stopping the printing device and before the next printing,
A first replenishment step of setting a constant ink key opening for each ink key region and replenishing the ink roller group with a constant amount of ink;
A second replenishment process sets the ink key opening corresponding to the image of the next printing, replenishing the ink to the ink roller group for each ink key region,
An ink preset method according to any one of claims 1 to 5.

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